Philip Grierson

Professor Philip Grierson, who has died aged 95, was that very rare combination - a world-class collector and a world-class scholar of coins. With his death, the Fitzwilliam Museum has lost one of its leading benefactors and Gonville and Caius College, Cambridge, has lost one of the last surviving ornaments of the great and dying tradition of the bachelor fellow resident in college.

Grierson was born in Dublin, where his surveyor father was a member of the Irish land commission. Philip was educated at Marlborough college, Wiltshire, went to Cambridge in 1929 and stayed for the rest of his life. At Caius, he was, in turn, junior fellow, college lecturer and director of studies in history, librarian, professorial fellow, president, life fellow and, finally, senior fellow.

From his austere set of rooms overlooking the market place, into which he moved in the mid-1930s, he produced an unrivalled flow of numismatic scholarship and entertained more undergraduates than almost any other member of his college. Scholars revered him for his learning and research; colleagues liked him for his encyclopaedic knowledge and sense of fun; and students, who were in awe of his longevity and his academic reputation, loved him because he shared their taste in food, films, music and literature.

Pizza, puddings and sausages were the kind of food he liked; populist films were his favourite fare; science fiction was his preferred literary diet. A library of more than 2,000 videos attracted an endless stream of students to his rooms; his liking for horror films almost equalled his liking for science fiction.

There was much more in his life to intrigue the young. He had been a communist sympathiser in the 1930s, although he never joined the party. He had flown to Germany to help Jewish scholars escape nazism in the 1930s. A great admirer of the Soviet Union, he refused to visit Spain while Franco was alive. He had rejected the offer of a CBE because he could not be bothered to dress up to go the palace. He could fly a plane but could not drive a car. He possessed a racing bike on which he swished round Cambridge like a teenager.

He played squash well into his 80s and finally gave up so as not to hurt the feelings of the soundly beaten undergraduates, some 60 years his junior. He claimed that in his younger days he walked from London to Cambridge, having missed his train. He regarded taxis as unacceptably expensive. The only example of travel indulgence recorded against him was an inability to resist flying to the US on Concorde.

Yet this was the man who formed the finest representative collection of medieval European coins in the world, some 20,000 specimens, which he has bequeathed to the Fitzwilliam. Estimates of their value vary but "between £5m and £10m" was Grierson's own, formed by prudent buying over 60 years, essentially from his salary as a university teacher.

His collection had a decisive effect on the direction of his research. He went up to Caius destined to read medicine, but immediately switched to history and did so well that he was awarded the Schuldham Plate, which is given to the leading college graduand chosen from all subjects. Although his earliest research had, rather surprisingly, been on ecclesiastical history and he had won the Lightfoot prize in theology, his work soon began to move decisively towards the use of coins as a major historical source.

Indeed, his academic reputation as a medieval historian rests on coins and their interpretation. He showed historians how little they understood of this fundamental historical source, and equally showed numismatists how little they knew of the world from which their coins have come. If his contribution to history has been large, his contribution to numismatics has been unique.

To numismatists, the Grierson Collection in the Fitzwilliam and the Byzantine Collection at Dumbarton Oaks, Washington, would alone justify the honours that their prime begetter has been given. However, since non-numismatists tend to disparage such collections as no more than a higher form of stamp collecting, it is worth pointing out how important the evidence provided by the coinage of past societies can be in the hands of a master.

A single example might suffice to underline Grierson's inspired use of numismatic evidence dramatically to resolve a major historical controversy. This was that which raged over the historian Henri Pirenne's long-standing explanation of the survival of gold coinage in the west until the early 9th century and its replacement by silver for the next 500 years. For Pirenne, the disappearance of gold was the last act of the decline of Rome in the west, and its cause was the depredations of Islam. In 1960, Grierson published a recondite article on the monetary reforms of Caliph Abd al Malik and their financial consequences, which showed that they included a decisive shift in the relative value of silver and gold in the Islamic world, bringing about the flight of silver to the west and gold to the east. In doing so, he illuminated a major factor in the rise of monometallism that endured for five centuries in western Christendom.

Such work demanded a rare combination of skills involving mathematics, statistics, metallurgical analysis and an enviable range of languages and detailed historical knowledge. With such skills, Grierson could bring professional rigour to a world well supplied with enthusiastic amateurs, and an impressively wide range and perspective to a subject all too often studied on local lines. His scholarship gave rise, among much else, to the five volumes published by Dumbarton Oaks, and the 15 volumes planned for the Fitzwilliam Collection. These books justified his international reputation.

At one time, Grierson held simultaneously three academic posts in three countries. In addition to his personal chair in Cambridge (1971-78), he was professor at Brussels (1948-81), adviser in Byzantine numismatics at Dumbarton Oaks (1955-98) and honorary keeper of coins at the Fitzwilliam Museum (from 1949 until his death).

In addition he was a syndic of both the University Library and the Fitzwilliam Museum, and chairman of the library syndicate (management board). He was literary director of the Royal Historical Society (1945-55), president of the Royal Numismatic Society (1961-66) and Ford's Lecturer in Oxford (1956-57). Made a fellow of the Society of Antiquaries (1949) and a fellow of the British Academy (1958), he was awarded a Cambridge LittD in 1971. He never married.

· Philip Grierson, numismatist and academic, born November 15 1910; died January 15 2006